Single-pixel imaging interferometer based on the synthesis of spatial coherence.

In this study, an interferometric method with conventional optical components without pixelated devices for the single-pixel imaging of a spatially incoherent light source is proposed. The tilting mirror performs linear phase modulation to extract each spatial frequency component from the object wave. The intensity at each modulation is detected sequentially to synthesize the spatial coherence such that the Fourier transform computation reconstructs the object image.

High-precision flat-plate reference infrared radiator using perfect blackbody composite with a microcavity structure.

Onsite reference infrared radiators are used to correct thermal imagers for noncontact fever screening in real time. We have developed a flat-plate reference radiator of the highest accuracy to enhance reliability of the fever screening. Our contact-durable blackbody composite with good heat transfer, which has a microcavity structured surface offering high emissivity (>0.

Micro-cavity perfect blackbody composite with good heat transfer towards a flat-plate reference radiation source for thermal imagers.

One of the key measures to secure reliable fever screening is to calibrate a thermal imager with an accurate flat-plate blackbody device in real time. We provide durable perfect blackbody plates with both high emissivity of >0.998 and good heat transfer, ideal for a high-precision reference radiation source.

Spatial axial shearing common-path interferometer for natural light.

A spatial axial shearing interferometer is proposed to obtain a mutual coherence function representing longitudinal spatial coherence of natural light. The modulation of the quadratic phase distribution displayed on a spatial light modulator generates a spatial axial shear without a radial one. Because the optical path lengths along the optical axis on the two paths are identical, the spatial axial shear can be greater than the coherence length derived by temporal coherence.

Large-area perfect blackbody sheets having aperiodic array of surface micro-cavities for high-precision thermal imager calibration.

We present a large-area perfect blackbody sheet, which would offer a planar standard radiator for high-precision thermal imager calibration. Polydimethylsiloxane (PDMS) sheets with nano-precision surface micro-cavity structures achieve both ultra-low reflectance (ultra-high emissivity close to unity) over the thermal infrared wavelengths and high durability to mechanical contact. The investigation on the geometrical parameters of the conical micro-cavities, that is, radii and aspect ratios (ratio of height to radius), confirmed that the PDMS blackbody sheet with a micro-cavity radius of ∼6 µm and an aspect ratio of ∼4 exhibits the optimum hemispherical reflectance of less than 0.

Radiometric temperature measurement by incoherent digital holography.

This study aims to demonstrate radiometric temperature measurement using incoherent digital holography. Since in-focus images of thermal radiations can be reconstructed at any distance, three-dimensional radiometric temperature can be measured. This requires an optical configuration with a fixed magnification to record an incoherent hologram that contains information about the spectral radiance of an object.

Optical configuration with fixed transverse magnification for self-interference incoherent digital holography.

The optical configuration proposed in this paper consists of a 4-f optical setup with the wavefront modulation device on the Fourier plane, such as a concave mirror and a spatial light modulator. The transverse magnification of reconstructed images with the proposed configuration is independent of locations of an object and an image sensor; therefore, reconstructed images of object(s) at different distances can be scaled with a fixed transverse magnification. It is yielded based on Fourier optics and mathematically verified with the optical matrix method.

Study of reference waves in single-exposure generalized phase-shifting digital holography.

The appropriate reference wave in single-exposure phase-shifting digital holography using a random-complex-amplitude encoded reference wave is experimentally investigated. Although the reference wave is generalized, the quality of reconstructed images depends on it. Furthermore, when the reference wave satisfies a certain condition, reconstructed images cannot be obtained in this method.

Single-exposure phase-shifting digital holography using a random-complex-amplitude encoded reference wave.

The improved single-exposure phase-shifting digital holography using a random-phase reference wave is proposed. The algorithm for obtaining a complex amplitude of an object wave is improved. In the proposed algorithm, the reference wave is treated as not a random-phase but a random-complex amplitude.

Single-exposure phase-shifting digital holography using a random-phase reference wave.

We propose a single-exposure phase-shifting digital holography based on a wave-splitting method using a random-phase reference wave. A random-phase reference wave gives random-phase distribution on the digital hologram. Using the amplitude and the phase distributions of the reference wave, the fully complex amplitude of the object wave is obtained.